A comparison of optic nerve dosimetry in craniospinal radiotherapy planned and treated with conventional and intensity modulated techniques

Rene, N.; Brodeur, M.; Parker, William; Roberge, David; Freeman, Carolyn R.

doi:10.1016/j.radonc.2010.09.022

Cited by 9 publications

(4 citation statements)

References 6 publications

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“…4,[19][20][21] We know that the optic nerves are surrounded by CSF to the back of the globe and that some RT planning techniques (tomotherapy) underdose this area unless it is specifically contoured as part of the CTV. 51 Neither our work nor the literature investigates whether there are meningeal reflections and CSF through the middle cranial fossa foramen, superior orbital fissure, ovale, rotundum and spinosum and this would be an interesting topic for further research.…”

Section: Discussionmentioning

confidence: 96%

Fast imaging employing steady-state acquisition (FIESTA) MRI to investigate cerebrospinal fluid (CSF) within dural reflections of posterior fossa cranial nerves

Noble¹,

Scoffings²,

Ajithkumar³

et al. 2016

BJR

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Objective: There is no consensus approach to covering skull base meningeal reflections-and cerebrospinal fluid (CSF) therein-of the posterior fossa cranial nerves (CNs VII-XII) when planning radiotherapy (RT) for medulloblastoma and ependymoma. We sought to determine whether MRI and specifically fast imaging employing steady-state acquisition (FIESTA) sequences can answer this anatomical question and guide RT planning. Methods: 96 posterior fossa FIESTA sequences were reviewed. Following exclusions, measurements were made on the following scans for each foramen respectively (left, right); internal acoustic meatus (IAM) (86, 84), jugular foramen (JF) (83, 85) and hypoglossal canal (HC) (42,45). A protocol describes measurement procedure. Two observers measured distances for five cases and agreement was assessed. One observer measured all the remaining cases. Results: IAM and JF measurement interobserver variability was compared. Mean measurement difference between observers was 20.275 mm (standard deviation 0.557). IAM and JF measurements were normally distributed. Mean IAM distance was 12.2 mm [95% confidence interval (CI) 8.8-15.6]; JF was 7.3 mm (95% CI 4.0-10.6). The HC was difficult to visualize on many images and data followed a bimodal distribution. Conclusion: Dural reflections of posterior fossa CNs are well demonstrated by FIESTA MRI. Measuring CSF extension into these structures is feasible and robust; mean CSF extension into IAM and JF was measured. We plan further work to assess coverage of these structures with photon and proton RT plans. Advances in knowledge: We have described CSF extension beyond the internal table of the skull into the IAM, JF and HC. Oncologists planning RT for patients with medulloblastoma and ependymoma may use these data to guide contouring.

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Section: Discussionmentioning

confidence: 96%

Fast imaging employing steady-state acquisition (FIESTA) MRI to investigate cerebrospinal fluid (CSF) within dural reflections of posterior fossa cranial nerves

Noble¹,

Scoffings²,

Ajithkumar³

et al. 2016

BJR

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“…CSI is technically challenging because of the planning target volume (PTV) length and the vital organs exposed. Nowadays, innovative techniques, such as three-dimensional conformal radiotherapy, proton beam, intensity modulated techniques, and tomotherapy, can be applied with great precision [ 9 , 10 ]. However, this patient had such a rapid improvement in the CNS with steroids, this might indicate that two extraordinarily rare events occurred in one person simultaneously: Askin's tumor of the rib and a different diagnosis in the CNS (such as CNS lymphoma, Langerhans’ cell histiocytosis, or CNS sarcoidosis) [ 11 , 12 ].…”

Section: Discussionmentioning

confidence: 99%

Suspected CNS Metastases of Askin's Tumor: Would You Irradiate the Neural Axis?

et al. 2012

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“…This can be explained by the fact that optic nerves, even when not specifically targeted during CSI, usually received a therapeutic dose with the lateral opposed beams of the classic 3D-conventional photon technique. However, Rene et al demonstrated that with modern intensity modulated radiation therapy (IMRT) planning techniques, there is a risk of underdosage of especially the anterior half of the optic nerves if not intentionally targeted, and that there is no margin for setup error regarding optic nerve dose coverage [7] .…”

Section: Introductionmentioning

confidence: 99%

Influence of eye movement on lens dose and optic nerve target coverage during craniospinal irradiation

Hoeben

Seravalli

Wood

et al. 2021

Clinical and Translational Radiation Oncology

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Optic nerves are part of the craniospinal irradiation (CSI) target volume. Modern radiotherapy techniques achieve highly conformal target doses while avoiding organs-at-risk such as the lens. The magnitude of eye movement and its influence on CSI target-and avoidance volumes are unclear. We aimed to evaluate the movement-range of lenses and optic nerves and its influence on dose distribution of several planning techniques. Methods: Ten volunteers underwent MRI scans in various gaze directions (neutral, left, right, cranial, caudal). Lenses, orbital optic nerves, optic discs and CSI target volumes were delineated. 36-Gy cranial irradiation plans were constructed on synthetic CT images in neutral gaze, with Volumetric Modulated Arc Therapy, pencil-beam scanning proton therapy, and 3D-conventional photons. Movement-amplitudes of lenses and optic discs were analyzed, and influence of gaze direction on lens and orbital optic nerve dose distribution. Results: Mean eye structures' shift from neutral position was greatest in caudal gaze; − 5.8±1.2 mm (±SD) for lenses and 7.0±2.0 mm for optic discs. In 3D-conventional plans, caudal gaze decreased Mean Lens Dose (MLD). In VMAT and proton plans, eye movements mainly increased MLD and diminished D98 orbital optic nerve (D98 OON ) coverage; mean MLD increased up to 5.5 Gy [total ΔMLD range − 8.1 to 10.0 Gy], and mean D98 OON decreased up to 3.3 Gy [total ΔD98 OON range − 13.6 to 1.2 Gy]. VMAT plans optimized for optic disc Internal Target Volume and lens Planning organ-at-Risk Volume resulted in higher MLD over gaze directions. D98 OON became ≥95% of prescribed dose over 95/100 evaluated gaze directions, while all-gaze bilateral D98 OON significantly changed in 1 of 10 volunteers. Conclusion: With modern CSI techniques, eye movements result in higher lens doses and a mean detriment for orbital optic nerve dose coverage of <10% of prescribed dose.

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A comparison of optic nerve dosimetry in craniospinal radiotherapy planned and treated with conventional and intensity modulated techniques

Cited by 9 publications

References 6 publications

Fast imaging employing steady-state acquisition (FIESTA) MRI to investigate cerebrospinal fluid (CSF) within dural reflections of posterior fossa cranial nerves

Fast imaging employing steady-state acquisition (FIESTA) MRI to investigate cerebrospinal fluid (CSF) within dural reflections of posterior fossa cranial nerves

Suspected CNS Metastases of Askin's Tumor: Would You Irradiate the Neural Axis?

Influence of eye movement on lens dose and optic nerve target coverage during craniospinal irradiation

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